Stock-Based Compensation (Summary of Restricted Stock Transactions) (Details)	3 Months Ended
	Mar. 31, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested stock awards outstanding at beginning of period (in shares)	1,053,842
Nonvested stock awards outstanding at end of period (in shares)	1,045,821
Time-vesting shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Awarded (in shares)	73,173
Released (in shares)	(59,035)
Forfeitures (in shares)	(4,575)
Performance-based shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Awarded (in shares)	142,154
Forfeitures (in shares)	(159,738)